Floral Biology and Pollination of Carpet Weeds, Glinus Lotoides L. and Glinus Oppositifolius (L.) Aug

Home , Glinus, Glinus lotoides, Molluginaceae, Zizeeria karsandra

Anales de Biología 40: 103-114, 2018 ARTICLE DOI: http: //dx.doi.org/10.6018/analesbio.40.12

Floral biology and pollination of carpet weeds, Glinus lotoides L. and Glinus oppositifolius (L.) Aug. DC. (Molluginaceae)

Maddala Sulakshana1 & Aluri Jacob Solomon Raju2 1 Department of Botany, Andhra University, Visakhapatnam 530 003, India. 2 Department of Environmental Sciences, Andhra University, Visakhapatnam 530 003, India.

Resumen

Correspondence Biología floral y polinización de las malas hierbas Glinus lotoides L. AJS. Raju y Glinus oppositifolius (L.) Aug. DC. (Molluginaceae) E-mail: [email protected] Glinus lotoides y G. oppositifolius son hierbas rastreras, esparci- Received: 5 January 2018 das, anuales. En ambas, las flores son muy pequeñas, actino- Accepted: 21 September 2018 morfas, bisexuales, protandradas, herkogamosas y facultativamen- Published on-line: 28 November 2018 te autógamas. Ambas especies exhiben antesis sincrónica y flores masivas para atraer a los polinizadores. Las abejas, hormigas, ma- riposas y trips polinizan las flores. La hercogamia excluye la autogamia espontánea, pero el evento de cierre de la flor facilita esta autogamia. En ambas especies, el fruto es una cápsula con semillas escrotiformes con estrofiolo; anemocoria, ombrohidrocoria e hidrocoria son funcionales. Las semillas germinan inmediatamen- te si el suelo tiene humedad. Las especies Glinus con fotosíntesis C3, autogamia facultativa y polifilia son capaces de crecer en hábi- tats secos y húmedos.

Palabras clave: Autogamia facultativa, Polinización por insectos, Anemocoria, Ombrohidrocoria, Hidrocoria.

Abstract

Glinus lotoides and G. oppositifolius are prostrate, spreading, annual herbs. In both, the flowers are very small, actinomorphic, bisexual, protandrous, herkogamous and facultatively autogamous. Both species exhibit synchronous anthesis and display flowers en masse to attract pollinators. Bees, ants, butterflies and thrips pollinate the flowers. Herkogamy precludes spontaneous autogamy but flower closing event facilitates autogamy. In both species, the fruit is a capsule with scrotiform strophioled seeds; anemochory, ombrohydrochory and hydrochory are functional. The seeds germinate immediately if soil has moisture. Glinus species with C3 photosynthesis, facultative autogamy and polyphily are able to grow in dry and moist habitats.

Key words: Facultative autogamy, Insect pollination, Anemochory, Ombrohydrochory, Hydrochory. 104 M. Sulakshana & AJS. Raju Anales de Biología 40, 2018

Introduction pollen output per flower and pollen-ovule ratio was done as per the formulas described in Cruden Little is known about the pollination ecology of (1977). Ten flowers each from five individuals Molluginaceae. In this family, nectar secreting tis- were used to test stigma receptivity. It was tested sue is present in almost all species. In several gen- with hydrogen peroxide from mature bud stage to era, showy sepals or petals have evolved, both of flower closure/drop as per Dafni et al. (2005). which strongly suggest entomophily (Watson & Seventy inflorescences were tagged prior to the Dallwitz 1992; Kubitzki et al. 1993). There is initiation of their flowering and followed for three some information on pollination ecology of Mo- weeks to record fruit and seed set rate in open- llugo L. species but not on Glinus L. genus pollinations. The fruit and seed morphological (Robertson 1928; Pax & Hoffmann 1934; Bogle characteristics were observed in detail to evaluate 1970; Lin et al. 1993; Ponnuchamy et al. 2014). their adaptations for dispersal by different means. Hence, the present study was contemplated to pro- Fields visits were made during rainy season to vide details of pollination biology of Glinus lo- note the aspects of seed germination and produc- toides L. and Glinus oppositifolius (L.) which tion of new plants. Anther dehiscence schedule usually grow in open habitats with little moisture and stigma receptivity period, and herkogamous and agricultural areas. Sastri (1956) reported that nature of stamens and stigmas were used to infer G. lotoides is widespread throughout the tropics the sexual system. Further, how the sexual system and subtropics, especially in Africa, Asia, Aus- facilitates both self- and cross-pollination was ex- tralia and South Europe. Teshome & Feyissa plained. Further, observations were also made to (2015) reported that G. lotoides is currently given evaluate as to how these positions preclude self- threatened status due to its regular harvest for pollination when flowers stay open. medicinal purpose in Ethiopia and Tanzania. Sahu Insects foraging at the flowers were observed et al. (2001) reported that G. oppositifolius is from morning to evening on four different days widely distributed in the Americas, tropical Asia, for their mode of approach, landing, probing tropical Africa and Australia. The objective of the behavior and contact with the floral sexual organs. present study is to provide details of phenology Bees and ants were identified with the representa- and floral biology of G. lotoides and G. oppositi- tive specimens available with the Department of folius to understand their reproductive aspects. Environmental Sciences, Andhra University, Visakhapatnam. Butterflies were identified by Materials and methods consulting the books of Kunte (2007) and Gunathilagaraj et al. (1998). For each species, an Wild patches of G. lotoides and G. oppositifolius area of 1 x 1 m of flowering individuals of a sin- growing in open habitats of Visakhapatnam and gle species consisting of approximately 450 flow- its surroundings in Andhra Pradesh, India ers was used for foraging activity. The foraging (17°42’N, 82°18’E) were selected for study be- visits of insects were recorded for 10 min at each tween March 2015 and May 2017. Field trips hour for the entire day and the data was tabulated were conducted to record phenological aspects. to record the foraging pattern and the percentage Ten inflorescences which were not initiated flow- of visits made by different insect categories. The ering on five plants were tagged and followed to pollen/nectar collection behavior of insects was record anthesis schedule and the timing of anther carefully observed to assess their role in effecting dehiscence. Twenty five fresh flowers were used pollination. Ten specimens of each insect species to record the floral morphological characters such were captured between 1400-1600 h and taken to as petals, stamens, ovules and relative positions of the laboratory. Each specimen was washed in the sex organs. Nectar could not be measured and an- drop of ethyl alcohol on a glass slide to separate alyzed due to its secretion in minute quantity pollen; then it was stained with aniline-blue and which was further depleted by thrips during ma- observed under microscope to count the number ture bud and flower life. Twenty mature, but un- of pollen grains present. From this, the average dehisced anthers, (two anthers each per number of pollen grains carried by each insect flower/plant from ten plants) were collected and species was calculated to know the pollen carry- examined for pollen output as per the protocol de- over efficiency. scribed in Dafni et al. (2005). The calculation of Fruit set rate was calculated by dividing the Anales de Biología 40, 2018 Pollination ecology of Glinus species 105 total number of fruits set with the total number of open sandy soils, cultivated fields and open waste flowers sampled and then value obtained was lands. In soils with enough moisture, they produce expressed in percentage by multiplying it with one well developed tap root and survive throughout hundred for each flower type separately for both the year producing flowers and fruits simultane- G. lotoides and G. opositifolius. The sample size ously or alternately. In both the species, the stem used for 8-12-stamened flowers in G. lotoides and is soft, succulent, pubescent and much-branched for 4-6-stamened flowers in G. oppositifolius was carpeting the soil with its foliage. In G. lotoides, provided in Table 4. Seed set rate was calculated the basal leaves are borne in a rosette form while by dividing the total number of seeds set with the the upper ones in verticillate form or rarely ar- average number of ovules per flower multiplied ranged opposite, and densely stellate tomentose. by the total number of fruits set and then the value In G. oppositifolius, the leaves are arranged in obtained was expressed in percentage by multi- pseudo-whorls of 3-6 or opposite to each other. plying it with one hundred for each flower type Flowering separately for both the species. In G. lotoides and G. oppositifolius, the flowering Results is profuse when soil is very damp which occurs during July-October due to monsoonal rains (Figs. The Plant 1a, 1f). In G. lotoides, the flowers are borne on 1.5 mm long stalks in axillary cymes and each G. lotoides and G. oppositifolius are low-growing cyme consists of 4.72 ± 1.3 (mean ± SD) flowers prostrate, spreading, annual herbs which grow in and each plant produces 82.5 ± 33.65 flowers. In

Figura 1. a-e Glinus lotoides. a. Fase de floración; b: Flor completamente abierta; c: Estambres y estigma; d: Cierre de flor a las 1800 h del día de la antesis; e: Capsula del fruro con estambres y estigma intactos tras marchitarse. f-j Glinus oppositifolius. f: Fase de floración; g: Flor; h: Estambres dehiscentes; i: Granos de polen; j: Ovario con tres estigmas. k-o Glinus lotoides: k: Haplothrips sp. alimentándose de néctar; l: Apis cerana recogiendo polen; m: Apis cerana recogiendo nectar; n: Camponotus sp. recogiendo nectar; o: Lycénido, Zizeeria karsandra, recogiendo nectar. Figure 1. a-e Glinus lotoides. a. Flowering phase; b: Fully open flower; c: Stamens and stigma; d: Flower closure at 1800 h on the day of anthesis; e: Fruit capsule with stamens and stigma intact in withered state. f-j Glinus oppositifolius. f: Flowering phase; g: Flower; h: Dehisced stamens; i: Pollen grains; j: Ovary with three stigmas. k-o Glinus lotoides: k: Haplothrips sp. feeding on nectar; l: Apis cerana collecting pollen; m: Apis cerana collecting nectar; n: Camponotus sp. collecting nectar; o: Lycaenid butterfly, Zizeeria karsandra collecting nectar. 106 M. Sulakshana & AJS. Raju Anales de Biología 40, 2018

G. oppositifolius, the flowers are borne on 3-7 yond the height of long stamens. In G. oppositi- mm long pedicels in axillary fascicles and each folius, the staminodes are 5 or 6, petaloid, white, fascicle consists of 7.5 ± 1.5 flowers and each bifid and anti-tepalous. In G. lotoides, the ovary plant produces 64.52 ± 41.28 flowers. (5 ± 0.23 mm long and 2.03 ± 0.17 mm wide) is green, pentacarpellary and pentalocular syncar- Flower morphology pous while in G. oppositifolius, the ovary (4.07 ± In both the species, the flowers are small, odour- 0.16 mm long and 2 ± 0.01 mm wide) is green, less, actinomorphic and bisexual (Figs. 1b, 1g). tri-carpellary and tri-locular syncarpous. In both They are 6.1 ± 1.28 mm long, 7.42 ± 1.25 mm the species, the ovules in each locule are arranged wide in G. lotoides and 3.51 ± 0.5 mm long, 8.57 on axile placentation. The ovule number varied ± 0.7 mm wide in G. oppositifolius. In both the from 181.9 ± 35.28 to 242.4 ± 35.14 in 8- and 12- species, the calyx and corolla are represented by stamened flowers in G. lotoides and from 115.5 ± perianth with 5 or rarely 6 tepals. The tepals are 7.1 to 137.7 ± 9.9 in 4- and 6-stamened flowers in succulent, free and arranged in quincuncial aesti- G. oppositifolius (Table 1). In both the species, the vation in both the species but they are 6.02 ± 0.19 ovule production trend showed that the number of mm long, 4.05 ± 0.2 mm wide, whitish green ovules produced gradually increased with a grad- adaxially and green abaxially, ovate-oblong and ual increase in the number of stamens per anther covered with stellate hairs in G. lotoides while and pollen out per flower but the variation is not they are 4.01 ± 0.2 mm long, 2.03 ± 0.2 mm wide, significant. The style is absent in both the species creamy white adaxially and brownish orange but G. lotoides has five greenish white stigmas abaxially, ovate-oblong and pubescent in G. op- while G. oppositifolius has three creamy white positifolius. The stamens are 8 to 12, free, white stigmas (Fig. 1j). In both the species, the stigmas and arranged in two whorls (Fig. 1c). The stamens are free, spreading, papillate, wet and shiny. of inner whorl close to ovary base are long and Floral biology form a short tube at the base around the ovary while those of the outer whorl are short. In G. lo- Mature buds open during 1400-1500 h in G. lotoides, the stamens of both whorls are usually toides and during 1200-1400 h in G. oppositi- anti-tepalous and occasionally alterni-tepalous. folius. Individual buds open gradually over a du- The flowers with 8-stamens constitute 14.28%, ration of 30 to 40 minutes in G. lotoides and 10 to those with 9-stamens 21.42%, those with 10-sta- 15 minutes in G. oppositifolius. In both species, mens 42.85%, 11-stamens 19.04% and 12-sta- the anthers dehisce by longitudinal slits during an- mens 2.38%. In G. oppositifolius, the stamen are 4 thesis. In G. lotoides, the pollen output per anther to 6, free but connate at the base, and alterni- varied from 1,193.85 ± 70.25 to 1,371.85 ± 65.76 tepalous. The flowers with 4-stamens constitute and from 10,974.85 ± 526.08 to 14,326.28 ± 5%, those with 5-stamens 80% and those with 6- 843.03 per flower in 8- to 12-stamened flowers re- stamens 15%. In both the species, the anthers are spectively (Table 1). In G. oppositifolius, the H-shaped, white, dithecous and versatile (Fig. 1h). pollen output per anther varied from 1,151 ± In G. lotoides, the staminodes are 5-7, petaloid, 67.22 to 957.33 ± 49.1 and from 4,604 ± 268.9 to white, bifid and usually alterni-tepalous but occa- 5,744 ± 295.1 per flower in 4 to 6-stamened flo- sionally in between short stamens; they extend be- wers (Table 1). In both the species, the pollen pro-

Percentage of Mean ± SD Mean ± SD Mean ± SD Pollen: ovule Flower type occurrence pollen output/anther pollen output/flower No. ovules/flower ratio Glinus lotoides 8-stamened 14.20 1371.85 ± 65.76 10974.85 ± 526.08 181.9 ± 35.28 60:1 9-stamened 21.42 1331.85 ± 91.46 11986.71 ± 823.21 196.7 ± 35.78 61:1 10-stamened 42.85 1304.57 ± 62.65 13045.71 ± 626.57 221.8 ± 40.67 59:1 11-stamened 19.04 1221.85 ± 61.36 13440.42 ± 674.99 230.2 ± 34.23 58:1 12-stamened 2.38 1193.85 ± 70.25 14326.28 ± 843.03 242.4 ± 35.14 59:1 Glinus oppositifolius 4-stamened 5 1151 ± 67.2 4604 ± 268.9 115.5 ± 7.1 40:1 5-stamened 80 1027 ± 55.5 5133 ± 277.5 128.6 ± 7.7 40:1 6-stamened 15 957 ± 49.1 5744 ± 295.1 137.7 ± 9.9 41.9: 1 Tabla 1. Aspectos del polen y óvulos de Glinus lotoides y Glinus oppositifolius Table 1. Pollen and ovule aspects in Glinus lotoides and Glinus oppositifolius. Anales de Biología 40, 2018 Pollination ecology of Glinus species 107 duction trend showed that the pollen output rate gradually increased with a gradual decrease in the number of stamens produced per flower. In G. lotoides, the pollen-ovule ratio varied from 58: 1 to 61:1 in 8- to 12-stamened flowers respectively. In G. oppositifolius, the pollen-ovule ratio is 40:1 and it is constant despite variation in the number of stamens and ovules. In both the species, the pollen grains are white, spheroidal, tricolporate, tri-zonoaperturate, colpal membrane densely gran- Figura 3. Actividad horaria de recolección de abejas y hormigas en Glinus lotoides. ulated, and tectum with scabrate ornamentation Figure 3. Hourly foraging activity of bees and ants on Glinus (Fig. 1i) but the grain size is 32.52 ± 4.28 µm in lotoides. G. lotoides and 29.34 ± 4.26 µm in G. oppositifolius. In both the species, the stigma is receptive from anthesis onwards and remains receptive until the noon of the following day. Further, the nectar is secreted in traces during mature bud stage. The tepals together with the staminodes, stamens and stigma close back completely by 1800 h on the same day (Fig. 1d) and remain in place in fertilized flowers until fruit dispersal. But, the un-fertilized flowers fall off after 7-10 days in G. lotoides and after 6-8 days in G. oppositifolius. Figura 4. Actividad horaria de recolección de licénidos en In G. lotoides, the fully open flowers show dif- Glinus lotoides. ferent positions of the stamens and the stigmas. Figure 4. Hourly foraging activity of lycaenid butterflies on G. lotoides. The stigmas are situated beyond the height of short stamens but below the height of long stamens. In G. oppositifolius, the stamens, staminodes and stigmas are situated at the same height. But, in both the species, the sex organs are spatially separated and precludes spontaneous autogamy during open state of the flower. However, during the closure of the flower, the closely spaced dehisced anthers of long stamens contact the stigmas facilitating spontaneous autogamy but its occurrence is dependent on the availability of Figura 5. Actividad horaria de recolección de abejas y hormigas pollen in the anthers. en Glinus oppositifolius. Figure 5. Hourly foraging activity of bees and ants on G. Foraging activity of insects oppositifolius. In G. lotoides and G. oppositifolius, thrips species, Haplothrips sp. (Amyot & Serville, 1843) (Thysanoptera: Thripidae) ovi-posited during early stage of floral bud (Fig. 1k). The larvae emerged from the eggs in synchrony with anthesis and nectar production in flowers. The larvae and adults foraged for pollen and nectar. Individual thrips were dusted with pollen during their movements within the flowers and carried 428 to 635 pollen grains of G. lotoides and 157 to 253 pollen grains of G. oppositifolius on their body setae, Figura 6. Actividad horaria de recolección de licénidos en Glinus oppositifolius. wings and legs. In both the species, the flowers Figure 6. Hourly foraging activity of lycaenid butterflies on G. were foraged between 1300/1400-1700 h with oppositifolius. 108 M. Sulakshana & AJS. Raju Anales de Biología 40, 2018 concentrated foraging activity between 1500-1600 ent visits. Ants were resident foragers and contin- h (Figs. 2-5). The foragers included bees which uously crawled all over the plant and accessed the visited for pollen and nectar, ants and butterflies floral base to collect nectar. Butterflies stretched which visited for only nectar. out their proboscis and inserted into the flower On G. lotoides, the bee foragers were Apis cer- base to collect nectar. All insect species collected ana (Fabricius, 1793) (Figs. 1l, 1m), Apis florea forage from several flowers of different cymes of (Fabricius, 1793), Trigona iridipennis (Smith, the same or different plants to collect the forage. 1854) and Ceratina sp. (Latreille, 1802). The ant The bees during pollen collection brushed against foragers included Camponotus sp. (Mayr, 1861) the stigmas with their ventral surface effecting (Fig. 1n) and Crematogaster sp. (Lund, 1831). sternotribic pollination. Further, the bees and also The butterfly foragers included only lycaenids, ants during nectar collection brushed against an- namely, Zizula hylax (Fabricius, 1775), Zizeeria thers and stigmas with their dorsal surface effect- karsandra (Moore, 1865) (Fig. 1o), Zizina otis ing nototribic pollination. The butterflies during (Fabricius, 1787), Freyeria trochylus (Forster, nectar collection contacted the stamens and stig- 1980), Chilades laius (Stoll, 1780) and Chilades mas with their proboscis and front side of head pandava (Horsefield, 1829) (Table 2). On G. op- and ventral surface of thorax and abdomen effect- positifolius, the bee foragers were A. cerana, A. ing sternotribic pollination. Their wings never florea (Figs. 6a, 6b), Ceratina sp. (Figs. 6c, 6d), contacted the stamens and stigma during nectar Ceratina smaragdula (Bingham 1897) (Fig. 6e), collection as they kept them in vertical position. Halictus sp. (Cockerell, 1897) and Megachile sp. On G. lotoides flowers, bees made 47%, ants 9% (Latrieille, 1802) (Fig. 6f). The ant foragers in- and lycaenids 44% of total foraging visits. On G. cluded Camponotus sp. and Crematogaster sp. oppositifolius flowers, bees made 60%, ants 5% The butterfly foragers included only lycaenids, and lycaenids 35% of total foraging visits. The namely, Z. hylax (Fig. 6g), Z. karsandra (Figs. 6h, body washings of insects collected from the flow- 6i), Z. otis (Fig. 6j), F. trochylus, C. laius and C. ers of both G. lotoides and G. oppositifolius dur- pandava (Table 2). In both the species, these in- ing peak foraging period revealed that all insects sects approached the flowers in upright position, carry pollen but bees carry the highest number of landed on the tepals and then probed for forage pollen grains. Further, the mean number of pollen collection. Bees first accessed anthers to collect grains varied with each insect species (Table 3). pollen and then moved to the flower base to col- The nectar secretion in traces and its depletion by lect nectar, if available in the same and/or differ- thrips during and after anthesis in both the plant

Figure 6. a-f. Glinus oppositifolius. a: Apis florea recogiendo polen; b: Apis florea recogiendo néctar; c: Ceratina sp. recogiendo polen; d: Ceratina sp. recogiendo néctar; e: Ceratina smaragdula recogiendo néctar; f: Megachile sp. recogiendo néctar; g-j Licénidos. g: Zizula hylax; h: Zizeeria karsandra; i: Zizeeria karsandra enestado de cópula; j: Zizina otis; k: Semillas de Glinus lotoides; l: Semillas de Glinus oppositifolius. Figure 6. a-f. Glinus oppositifolius. a: Apis florea collecting pollen; b: Apis florea collecting nectar; c: Ceratina sp. collecting pollen; d: Ceratina sp. collecting nectar; e: Ceratina smaragdula collecting nectar; f: Megachile sp. collecting nectar; g-j Lycaenid butterflies. g: Zizula hylax; h: Zizeeria karsandra; i: Zizeeria karsandra in mating state; j: Zizina otis; k: Glinus lotoides seeds; l: Glinus oppositifolius seeds. Anales de Biología 40, 2018 Pollination ecology of Glinus species 109

Order/Family Insect species Glinus lotoides Glinus oppositifolius Forage sought Hymenoptera Apidae Apis cerana F. + + Pollen + Nectar Apis florea F. + + Pollen + Nectar Trigona iridipennis Smith + - Pollen + Nectar Ceratina smaragdula F. - + Pollen + Nectar Ceratina sp. + + Pollen + Nectar Halictidae Halictus sp. - + Pollen + Nectar Megachilidae Megachile sp. - + Pollen + Nectar Formicidae Camponotus sp. + + Nectar Crematogaster sp. + + Nectar Thysanoptera Thripidae Haplothrips sp. + + Pollen + Nectar Lepidoptera Lycaenidae Zizula hylax F. + + Nectar Zizeeria karsandra Moore + + Nectar Zizina otis F. + + Nectar Freyeria trochylus Freyer + + Nectar Chilades laius Stoll + + Nectar Chilades pandava Horsfield + + Nectar Tabla 2. Lista de insectos polinizadores de Glinus lotoides y Glinus oppositifolius. Table 2. List of insect pollinators on Glinus lotoides and Glinus oppositifolius.

Insect species Sample size (N) Glinus lotoides Glinus oppositifolius Number of pollen grains Number of pollen grains Range Mean S.D. Range Mean S.D. Apis cerana 10 92-307 208.2 55.45 87-236 161.5 46.6 Apis florea 10 78-252 167.1 56.83 66-214 140.5 42.9 Trigona iridipennis 10 43-214 129.2 46.26 ------Ceratina smaragdula 10 ------68-164 115.9 24.8 Ceratina sp. 10 35-94 64.1 17.44 41-117 84.2 21.6 Halictus sp. 10 ------27-63 44.1 9.1 Megachile sp. ------43-102 74.8 16.1 Camponotus sp. 10 27-58 39.4 8.59 22-45 31.3 7.4 Crematogaster sp. 10 23-46 34.5 6.43 13-34 25.1 6.4 Zizula hylax 10 8-31 21.4 6.29 11-38 26.8 7.2 Zizeeria karsandra 10 15-40 27.8 7.40 9-46 28.8 9.2 Zizina otis 10 11-29 20.8 5.24 14-30 23.1 5.1 Freyeria trochylus 10 10-38 25.4 7.4 7-29 19.3 6.1 Chilades laius 10 12-34 23.3 6.37 10-35 24.8 7.0 Chilades pandava 10 10-42 28.4 8.27 12-41 28.1 7.2 Tabla 3. Polen registrado en lavados de cuerpo de insectos obtenidos en Glinus lotoides y Glinus oppositifolius. Table 3. Pollen recorded in the body washings of insects on Glinus lotoides and Glinus oppositifolius. species appeared to be driving the insects to visit 85% to 93% in 8- to 12-stamened flowers respec- as many flowering cymes as possible to quench tively (Table 4). In G. oppositifolius, natural fruit their thirst for nectar. Such a foraging behavior set rate varied from 88% to 92% while seed set was considered to be facilitating the promotion of rate varied from 88% to 91% in 4- to 6-stamened cross-pollination. flowers respectively (Table 4). Fruit is a loculicidal 5-valved capsule, 6.05 ± 0.75 mm long and Fruiting ecology and seed dispersal 4.1 ± 0.64 mm wide in G. lotoides while it is an The pollinated and fertilized flowers grow contin- ellipsoid loculicidal 3-valved capsule, 5.5 ± 0.5 ually and produce fruits within 8-12 days in G. lo- mm long and 2.1 ± 0.2 mm wide in G. oppositi- toides and 7-10 days in G. oppositifolius. In both folius. In both the species, the fruit is stalked, the species, the stamens and stigmas are persistent membranous and densely pubescent. In G. lo- and remain inside due to the closure of the flower toides, the seeds are small, reniform, smooth, 0.7 (Fig. 1e). The tepals bulge gradually and protect mm long and 0.5 mm wide, initially red and fi- the bulging ovary in which the seeds form and nally dark brown and have a white aril of funicu- mature. In G. lotoides, natural fruit set rate varied lar origin developed into elongate filiform stro- from 88% to 92% while seed set rate varied from phiole (Fig. 6k). In G. oppositifolius, the seeds are 110 M. Sulakshana & AJS. Raju Anales de Biología 40, 2018

Flower type Number of flowers sampled Number of flowers set fruit Fruit set (%) Seed set (%) Glinus lotoides 8-stamened 50 45 90 85 9-stamened 60 53 88 87 10-stamened 110 98 89 90 11-stamened 45 41 91 92 12-stamened 25 23 92 93 Glinus oppositifolius 4-stamened 61 54 88 88 5-stamened 225 206 91 90 6-stamened 105 97 92 91 Tabla 4. Proporción entre los conjuntos de frutos y semillas de Glinus lotoides y Glinus oppositifolius. Table 4. Natural fruit and seed set rate in Glinus lotoides and Glinus oppositifolius. small, sub-reniform, granulose, 0.9 mm long and Ronse De Craene (2010) stated that Glinus 0.7 mm wide, reddish-brown and have a white aril species have five sepals in quincuncial aestiva- of funicular origin developed into extensively tion. In the present study, G. lotoides and G. curved scrotiform strophiole (Fig. 6l). In both the oppositifolius have been found to have five tepals plant species, the seeds are arranged in two rows as common and six tepals as rare. The study also in each locule. Dry capsules of both the species indicates that the word "tepal" is the appropriate break open when tepals are wet and expose the word since it acts as petal adaxially and sepal seeds. But the seeds remain so and gradually sepa- abaxially. This is further substantiated by two dif- rate and fall to the ground on their own on clear ferent colours displayed on adaxial and abaxial sunny days. In dry season, when the capsules are surface. The tepals are whitish green on adaxial ripe, the plants die, dry out and become brittle. In surface and green abaxial surface in G. lotoides this state, the base of the stem breaks off and it is and creamy white on adaxial surface and brown- more so when high winds prevail. Then, the plant ish orange on abaxial surface in G. oppositifolius. parts roll readily and fruit and seeds disperse to In Glinus species, the stamen number is unsta- other areas. On rainy days, drops of water falling ble and varies from five to several series which on the distal opening after the locules are filled include outer staminodes also (Hoffman 1994). with rain water result in an explosive expulsion of The staminodes are petaloid, represent the sta- water droplets and seeds. Further, water also dis- mens that lost their function as producers of fertile perses seeds fallen on the soil during rainy season. pollen and antisepalous replacing a fertile stamen Therefore, seed dispersal is characteristically or alternisepalous as an appendage of upper sta- anemochorous, ombrohydrochorous and hydro- men (Weberling 1989; Brockington et al. 2013). chorous in both G. lotoides and G. oppositifolius. Ronse De Craene (2010) reported that in G. lotoides the alternisepalous whorl is complete Discussion with staminodes and odd stamen is opposite to petals. Sharma (1963) mentioned that G. lotoides G. lotoides and G. oppositifolius are prostrate, flowers produce rarely more than five stamens spreading, annual herbs that carpet the ground in while G. oppositifolius produce 10-13 stamens in open sandy soils and agricultural lands. They oc- three whorls. He also suggested a tendency for cur throughout the year and show vegetative, reduction with the loss of the outer stamen whorl flowering and fruiting phases in different areas. in androecium. In the present study, G. lotoides But, their robust growth, profuse flowering and flowers had 8-12 antitepalous functional stamens fruiting is confined to wet season. The flowers in two whorls and 5-7 alternitepalous staminodes borne in axillary cymes in G. lotoides and axillary in outer whorl. G. oppositifolius flowers had 4-6 fascicles in G. oppositifolius stand erect above the alternitepalous functional stamens in one whorl foliage and display their prominence. In both the and 5-6 antitepalous staminodes in outer whorl. In species, the stems produce many branches and both the species, the staminodes are petaloids each branch produces several cymes or fascicles. indicating the fusion of two adjacent stamens that Since the plants usually grow as green carpets, the lost the function of producing viable pollen in simultaneous display of several flowers from indi- course of the evolution of flowers. These stamin- vidual plants and from the entire population(s) odes are integral features of floral morphology could enhance their attraction to insect pollinators. and appear to have evolved to serve as attractants Anales de Biología 40, 2018 Pollination ecology of Glinus species 111 to pollinators, reduce self-pollination rate and deprived environment, especially in habitats optimize the available nutrients for enhanced where other herbaceous plant species flower reproductive output in water and nutrient deficient simultaneously, show anthesis during forenoon habitats. Further, the production of staminodes period and attract insect pollinators with their appears to be an adaptation to reduce pollen pro- vivid floral colors. Glinus species provide suffi- duction per flower, increase efficiency of pollen cient forage for insect pollinators in the afternoon dispersal by limiting pollen removal by individual period and accordingly bees, ants and lycaenid pollinators and enable precise contact between butterflies collect forage and pollinate flowers. pollinators and pollen presenters or pollinators Since bees and butterflies are active throughout and stigmas. Therefore, the petaloid staminodes day, they soon switch to fresh forage available in are evolved to perform different roles in the flow- the habitat. Glinus species with afternoon anthesis ers and are unique for Glinus within Mollugi- readily provide forage, and bees and butterflies naceae (Stebbins 1974; Ronse De Craene & Smets begin to shift to these floral sources and concen- 1993, 1995; Ronse De Craene 2013). trate on forage collection from them. Therefore, Hammer (1995) reported that different popula- afternoon anthesis in Glinus species could ensure tions of Aizoaceae growing in the same habitat insect pollination and reciprocate the insect polli- exhibit synchrony in flowering time. The period nators with pollen and/or nectar. of flowering is usually short and the flowers show Watson & Dallwitz (1992) stated that Mollugi- repeated opening but this phenomenon is naceae members are entomophilous. These restricted to a certain period of the day. Groen & authors considered nectar secreting tissue and Van Der Maesen (1999) observed that the mixed showy tepals in several species as adaptations for populations of Aizoaceae genera, Bergeranthus entomophily. In Glinus species, the floral charac- Schwantes, Faucaria Schwantes and Ortho- ters such as the erect position of flowers above pterum L. Bolus flower simultaneously. These foliage, adaxial surface of the tepals, petaloid authors suggested that such a synchrony in flow- staminodes and nectar secreting tissue between ering in these genera in the same habitat collec- the ovary base, connate part of staminal filaments tively enable them to enhance their floral attrac- and scabrate ornamentation of pollen grains tion to pollinators. In the present study, it is found appear to be adaptations for insect pollination. that Glinus species form mixed and distinct popu- The bees while collecting pollen and butterflies lations in the same and different habitats depend- while collecting nectar effect sternotribic pollina- ing on soil moisture and nutrient conditions. tion. Further, the bees and ants while collecting These species exhibit synchrony in flowering by nectar effect nototribic pollination. In both G. opening flowers in the afternoon. Further, the lotoides and G. oppositifolius, the pollen output flowers are too small, lack corolla, tepals not per anther varies with the number of functional vividly coloured and stay open for a brief period, stamens present in the flowers; it increases with a for three hours in G. lotoides and four hours in G. decrease in the stamen number. The pollen output oppositifolius for visitation by insects. Therefore, per flower in G. lotoides is more than double the the synchrony in anthesis schedule and massive amount produced per flower in G. oppositifolius. floral display appear to be imperative for them to The variation in pollen production in these plant attract pollinators during the brief period of open species is partly attributable to the number of sta- state of flowers. mens produced. The varied amount of pollen out- Peter et al. (2004) reported that the tempera- put in the flowers of the same and different inflo- ture and relative humidity are probably important rescences on the same plant drives the pollen col- cues determining flower opening in the afternoon. lecting bees to visit the flowers across population The specific timing of anthesis in the late after- (s) in search of more pollen collection and such a noon is a likely mechanism to filter out generalist foraging activity contributes to both self- and pollinators most active at midday, rather targeting cross-pollination. The nectar secreted in traces in specific group of insects, primarily bees, still both the species and nectar removal by thrips active in the late afternoon. The present study species, Haplothrips also drives the nectar collect- indicates that afternoon anthesis in Glinus species ing bees, ants and lycaenid butterflies to visit is probably evolved in course of time to avoid flowers across population(s) due to which both competition for pollinators in a pollinator- self- and cross-pollinations occur. Glinus species 112 M. Sulakshana & AJS. Raju Anales de Biología 40, 2018 appear to be important sources of pollen for bees, many ovules as possible through spontaneous especially for honey bees. Saad-Aldeen (2014) autogamy or vector-mediated pollination. This sit- also noted that G. lotoides is an important pollen uation is reflected in the natural fruit and seed set source for honey bees in Radom area, South Dar- rates in both plant species. The highest fruit and fur State, Sudan. Further, these plant species in seed set rates and the lowest pollen-ovule ratios the study area are important nectar sources for recorded in G. lotoides and G. oppositifolius indi- ants and lycaenid butterflies. Among butterflies, cate that they are facultatively autogamous but lycaenids are the smallest, low-flying and appro- breeding test is required for confirmation. priate pollinators for prostrate herbs such as Gli- Bittrich (1990) reported that Molluginaceae nus species. members produce capsules with many seeds and In both Glinus species, the flowers are protan- the capsules dehisce loculicidally to expose seeds. drous because there is a brief gap between anther In G. lotoides, the capsules open when moistened dehiscence and commencement of stigma recep- with the aid of expanding keels. In the present tivity. Since both male and female sexes mature study, in G. lotoides and G. oppositifolius, the fer- almost at the same time, the flowers in these plant tilized flowers produce fruits within a week or species can be stated as homogamous. Further, the two. The fruit is a capsule but it is 5-valved in G. stamens and stigmas are spatially separated in lotoides and 3-valved in G. oppositifolius. In dry both the species; such a situation suggests that the season, plants with ripe and dry capsules break off flowers are also herkogamous. Herkogamy does which are then dispersed by wind. Dry capsules not facilitate the occurrence of spontaneous auto- break open loculicidally when tepals become wet gamy despite the flowers being homogamous. and then expose the seeds. However, the seeds However, the thrips emerging from the floral buds remain attached to the base of the perianth. In during anthesis and their movements in the flow- both the species, the seeds exposed from the cap- ers after anthesis for pollen and nectar collection sules fall to the ground on clear sunny days. On could result in autogamy. They also bring about rainy days, water drops find their way into the geitonogamy due to their migration to different fruit through the distal opening and the fruit filled inflorescences on the same plant for forage collec- with water expels both water and seeds explo- tion and xenogamy due to their migration to other sively. Further, seeds fallen on the ground disperse conspecific plants for forage collection. Further, through surface water runoff during rain fall. the movement of tepals together with stamens Therefore, G. lotoides and G. oppositifolius towards the pistil during flower closure facilitates exhibit anemochory, ombrohydrochory and hydro- contact between the sex organs and effects sponta- chory. neous autogamy if pollen is still available in the Glinus species produce seeds with a white aril dehisced stamens. Further, the tiny thrips by mov- of funicular origin and the latter develops into ing into the closed flowers from apical portion elongate, filiform strophiole (Narayana 1962; and from sides may effect geitonogamy or Hofmann 1973). Glinus genus is characterized by xenogamy. Therefore, G. lotoides and G. oppositi- its seeds with a filiform appendaged aril and indu- folius while keeping the options open for sponta- mentum of often stellate hairs (Ronse De Craene neous or vector-mediated selfing exhibit polyphily 2013). In this study, G. lotoides has been found to involving bees, ants, butterflies and thrips as polli- produce small reniform, smooth and dark brown nators. seeds and its seeds have a white aril of funicular In the present study, Glinus species show vari- origin developed into elongate filiform strophiole. ation in the number of carpels and ovules per In G. oppositifolius, the seeds are small, sub-reni- flower. The flowers of G. lotoides produce five form and reddish-brown with a white aril of funic- carpels while those of G. oppositifolius produce ular origin formed into extensively curved scroti- three carpels. Likewise, the number of ovules also form strophiole. The presence of filiform or scro- varies depending on the number of stamens and tiform strophiole in Glinus species appears to be pollen output per flower; the ovules are relatively an adaptation for seed dispersal by ants (Costea et more in G. lotoides than in G. oppositifolius. This al. 2003). But, ants have not been found to use the ovule production trend indicates that the pollen strophiole as food and carry seeds of these output increases with an increase in ovule number species. However, further studies if taken up on in order to provide sufficient pollen to fertilize as this aspect may throw more light either to confirm Anales de Biología 40, 2018 Pollination ecology of Glinus species 113 or refute this observation. nation Biology. Cambridge, UK: Enviroquest Ltd. Balcha (2009) reported that G. lotoides has Groen LE & Van Der Maesen LJG. 1999. Revision of the genus Faucaria (Ruschioideae: Aizoaceae) in South short seed viability period. Teshome & Feyissa Africa. Bothalia 29: 35-58. (2015) also reported that this species propagates Gunathilagaraj K, Perumal TNA, Jayaram K & Ganesh by seed but short period of seed viability and poor Kumar M. 1998. Field Guide: Some South Indian seed germination percentage are the limiting fac- Butterflies. 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